Means for manufacturing printing forms



Sept. 5, 1944. R KAULEN 2,357,476

MEANS FOR MANUFACTURING PRINTING FORMS Original Filed June 3. 1937Patented Sept. 5, 1944 UNITED. STATES PATENT oFFlcs assure P RobertKaulen, Loevenich-Cologne, Germany, as-

signor to the firm Switzerland of Eden A. G., Zing-Zurich,

4 Claims.

This invention is a division from U. S. application Serial No. 146,228flied June 3, 1937, and relates to a device for coating bodies ofsubstantially cylindrical shape, and is more particularly concerned withmeans for uniformly coating printing cylinders with a light-sensitivecolloidal coating.

In order to obtain faultless prints, it is important that a thinsensitive coating be uniformly and evenly spread over the face of theprinting roller around its entire circumference.

'It is a diflicult task to apply such an "endless coating upon thesurface of a cylinder, and it is an object of the invention to provide adevice which enables the operator to fulfill this task without failure.It is a further object of the invention to provide for this purpose adevice of relatively simple structure.

Further objects of the invention will be apparent from the detaileddescription of the invention. Devices of the kind in question usuallycomprise a container which holds the coating fluid, and supporting meansfor the cylinder which is to be provided with the coating. Ac-

cording to the invention, the container is provided at the top with anarrow opening through which only a narrow area of the cylinder contactsat a time with the coating fluid. Spreading of the fluid over the wholecircumference of the cylinder is then achieved by rotating the cylinder.The supporting means therefore cooperate with means for rotating thecylinder around its axis, the cylinder being supported with its axisextending in horizontal direction while the coating takes place. Therotating means may be adjusted so asto effect 'slow rotation of thecylinder. Preferably the container has the shape of a channel, i. e. thecontainer is a narrow box the upper side of which is open.

In order to avoid creeping of the fluid, it is advisable to provide theside walls of the container with inclined upper faces, 1. e. the upperfaces bordering the opening of the container may slope downwardly andoutwardly.

The container with the liquid bath and the supporting means are soarranged relative to each other that the cylinder only just touches thsurface of the bath while the coating takes place. Contact of thecylinder face with the surface of the liquid may be established by anysuitable means. Preferably, means are provided for raising and loweringthe bath into and out of contact with the cylinder. Such means mayconsist of a device of any well-known suitable structure for lifting andlowering the container,

' within the container.

In order to ensure proper contact of thliquid with the roller, it isadvisable to provide for a compensating reservoir which communicates'with the container in such a manner that the latter is always keptfllled.

The formation of the coating on the cylinder may be improved by holdingthe cylinder and the fluid at about the same elevated temperature whilethe coating takes place. The device according to the invention maytherefore be equipped with suitable means for heating or preheating thecylinder as ell as the fluid, and with temperature-contro iingapparatus. Heating means and controlling apparatus of any well-knownsuitable structure ay be used for this purpose.

As already stated, the rotating means should cause very slow rotation ofthe cylinder, this being of particular importance for attaining aperfectly uniform coating. The speed of rotation should be so chosenthat a single rotation requires several minutes, preferably about fiveminutes.

The enclosed drawings illustrate by way of example one embodiment of theinvention which, however, is not limited to the details shown in thatembodiment.

Fig. 1 shows schematically a vertical section through a coating deviceaccording to the invention.

Fig. 2 is a plan view, with parts in section, and parts broken away, ofthe coating bath container and associated means.

Fig. 3 is a fragmentary sectional elevational view showing the apparatusin coating position.

The device schematically illustrated in Figs. 1 and 2, enables toprovide printing cylinders with a substantially uniform coating, with thonly exception, if any, of a narrow border line where the coating mayperhaps become a little thicker than on the other area. At the sametime, this device makesit possible to keep the coating free from dust,without requiring encumbering space. For attaining this purpose, thecylinder is not dipped to any substantial extent into the fluid, but itis rotated only along the top opening of the container filled with thefluid in such a way that its surface is just touching the surface of thecoating fluid and the fluid is preferably drawn out of a channel-shapedor groove-like container by way of adhesion of the fluid to therevolving cylindenor by the action' of the surface tension of the fluid.Separation of the cylinder and the bulk of the coating fluid can beeffected very uneven streak whatever will be formed on -the cylinder. Inorder to still further restrict formation of an uneven streak ofseparation on the cylinder, the opening at the top of the fluidcontainer may be rather narrow, while its length should at leastcorrespond to the length of the cylinder which is to be coated.

Since only a rather narrow part of the surface of the coating fluid isleft free, and since furthermore this part is still to some extentprotected by the cylinder arranged above it, there is very little dangerof dust getting on to the surface of the coating liquid. Additionalprotective means may be provided such as wipers arranged in front of thecoating channel or groove, which glide on the cylinder surface,thoroughly removing any dust from the surface as the cylinder revolves,whilst behind the coating channel a protecting plate may be fixed whichprevents access of dust to the freshly coated area of the cylinder.

As shown in Fig. 1, the cylinder I to be coated has its axial trunnionsla adapted to be mounted on bearings, preferably in the form of rollerslb, carried by a suitable supporting structure lc. Means such as themotor driven belt and pulley mechanism Id, le are provided for rotatingcylinder l. Vertically beneath the cylinder l to be coated, a groove orchannel 2 is arranged which is open at the top and extends over theentire length of the cylinder I. If desired, a cover 2 may be providedfor closing the top opening when the device is at rest. The bottom partoi. the channel 2 is connected to a compensating reservoir ofconveniently the same horizontal length as the channel 2 (see Fig. 2),communicating tubes 4 connecting reservoir 5 and container 2. Tubes 8(Fig. 2) feed the colloidal fluid to the compensating reservoir I from atank not shown. The interior of the compensating reservoir 5 which maybe closed by a detachable cover "I,'is provided with a number ofoverflow tubings I, the tops ofwhich are exactly on the same level withthe upper opening or brim of the channel 2. Thus channel 2 will remainpermanently filled up to the brim as long as suflicient fluid is fedfrom the tank to reservoir 5.

As may be seen from Fig. 1, the top border of the channel 2 is bevelledon either side, as shown at 9. This willprevent any liquid fromcollecting on these edges, which liquid otherwise might come intocontact with the cylinder and might cause unevenness of the coating. Thesaid bevels need, however, not reach the inner edges of the channel.

Suitable means for bringing the cylinder in and out of contact with thesurface of the liquid bath filling container 2, may be provided,

a as well as means for regulating the temperature of the bath and of thecylinder respectively. According to the embodiment shown in thedrawings, the apparatus consisting of the coat-' 1 paratus supported'byit may be raised or lowered towardor swayfrom cylinder l bymean'softher'ackandpinionmeans llb, lie.

stat not shown. The liquid drains of! through is In front of the groove2, leather-wipers II, II are arranged which extend over the whole lengthof the cylinder. In the embodiment shown in Figa. 1 and 2; these wipersII, II are fitted to rods l'l, ILfixed to a joint or hinge II, which isconnected to a counter-weight 20. Instead of the counter-weight,obviously also springs may be employed.

At the opposite side of the channel 2 and adiacent casing ll, a wall 2|is arranged which suitably extends up to cylinder I, as shown in Fig. 1,thus closing off the space between the cylinder and easing II and actingas a dustguard. Wall 2| may be hinged at 23, and may be detachably fixedto casing II by means of thumb screws 22. 1

If desired, the wipers It, I. may be replaced by a second correspondingwall protecting against dust, or such a wall may be arranged alongsidethe wipers l5, I.

For using this device, the casing I0 is first filled with water or withany other suitable liquid having the desired uniform temperature, andalso the compensating reservoir 5 is filled with the coating fluid. Thelatter passes from reservoir 5 through the tubes 4 to the coatingchannel 2 and fills it up to the brim, the level of which corresponds tothe top of the overflow tubes -8. Till this moment the cover 3 of thecoating channel 2 may be kept closed. When the cover is removed, eitherthe cylinder l, which, if desired, may be preheated by suitable means,including a thermostatically controlled current of warm water fedthrough the cylinder from warm water pipe lia, is lowered down towardsthe brim of channel 2, or the latter is raised towards the cylindertogether with casing l0, e. g. by means of the adjusting screws l2,until the surface of the fluid in channel 2 comes into contact with thecylinder as indicated in Fig. 3. The slowly revolving cylinder l takesup the coating fluid from the groove 2 in consequence of the adhesion orsurface tension of said fluid, and the cylinder is thus evenly coated,whilst from the not shown reservoir a corresponding quantity of coatingfluid flows into the com-. pensating reservoir 5.

In most cases coating is completed after one complete revolution of thecylinder in contact with the bath of liquid has taken place. Separatingmeans (not shown) of any convenient structure then cause separation ofthe cylinder surface and the surface of the bath, for instance bylowering channel 2.

Usually the bath consists of a photosensitive solution such as asolution of bichromated gelatine. However, other coatings such as avarnish or lacquer, may be applied by means of the same device.

I claim:

1. A device for uniformly coating bodies of substantially cylindricalshape with a sensitive layer for the manufacture of printing forms,comprising a container provided at the top with an elongated narrowopening and adapted to be filled with liquid for forming a sensitivelayer, the upper faces of the side walls of the container bordering thenarrow opening sloping downwardly and outwardly, means for rotatably Spporting the body to be coated above said container and in verticalalignment with said stationary means for rotatably supporting the bodyto be coated above said container and in vertical alignment with saidnarrow opening, means for raising and lowering said container whereby tobring a linear portion of the peripheral surface of said body intoliquid-contacting relationship with respect to said narrow openingwithout dipping into the liquid to any substantial amount, and means forrotating said body.

3. A device for uniformly coating cylinders with a light-sensitive layerfor the manufacture of printing forms, comprising a container containinga bath of a light-sensitive colloidal fluid,

said container having the shape of a narrow.

channel and the upper faces of the side walls of the channel beinginclined in downward and" outward direction; means for rotatablysupporting the cylinder to be coated above said channel, the axis of thecylinder extending in horizontal direction and the said supporting meansbeing arranged in such a manner that the said cylinder during thecoating step only just touches the surface of the said bath; means forrotating said cylinder while the coating takes place, wipers cooperatingwith the face of the cylinder for removing dust therefrom, said wipersbeing arranged to resiliently lcontact said face along substantially itswhole length and shortly before the respective portion of the facetouches the surface of the fluid bath, and means for separating saidcylinder face from said surface of the bath after the coating has takenplace.

4. A device for uniformly coating printing cylinders with a photosensitive layer, comprising a narrow, open container filled up to thebrim with a bath of a solution of bichromated gelatine, means forrotatably supporting the cylinder to be coated above said container,means for heating said cylinder, means for heating said bath, means forlowering and raising said container and the bath, whereby a narrow areaof the face of the cylinder can contact the surface of the bath, andmeans for rotating said cylinder.

ROBERT KAULEN.

